Physical Fitness and All-Cause Mortality in Older Adults

1. Better physical fitness was associated with lower mortality

Higher fitness was consistently associated with lower all-cause mortality across the physical assessments.

Importantly, these relationships remained after adjustment for multiple health and demographic factors, including self-reported physical activity.

This suggests that objective physical performance provides information about health and mortality risk beyond simply asking how physically active someone is.

2. Balance and agility showed some of the strongest associations

Among the individual tests, the strongest associations were seen for balance and agility.

Participants in the highest-performing fifth on the 8-foot up-and-go test had an adjusted hazard ratio of 0.41 compared with those in the lowest-performing fifth.

This corresponds to an approximately 59% lower relative hazard of death during follow-up.

For the one-leg stance test, the corresponding adjusted hazard ratio was 0.50, or approximately 50% lower relative hazard.

These are associations between measured performance and subsequent mortality. They do not mean that improving performance on these tests would itself reduce mortality by 59% or 50%.

3. Lower-body strength was strongly associated with survival

Lower-body strength was assessed using the 30-second chair stand test — the number of times a participant could rise from a chair without using the arms.

Participants in the highest-performing fifth had an adjusted hazard ratio of 0.55 compared with those in the lowest-performing fifth.

This corresponds to approximately 45% lower relative hazard of death during follow-up.

Lower-body strength is particularly relevant to functional aging because it contributes to standing, walking, stair climbing and independent mobility.

4. Cardiorespiratory fitness was also strongly associated with mortality

Cardiorespiratory fitness was assessed using the 2-minute step test.

Participants in the highest-performing fifth had an adjusted hazard ratio of 0.58 compared with those in the lowest-performing fifth — approximately 42% lower relative hazard of death.

Upper-body strength and flexibility were also associated with mortality, but their associations were weaker than those observed for balance and agility, lower-body strength and cardiorespiratory fitness.

5. Overall multidimensional fitness showed the strongest association

The researchers combined all seven assessments into a composite fitness index.

Participants in the highest fifth of overall fitness had an adjusted hazard ratio of 0.39 compared with those in the lowest fifth.

This represents approximately 61% lower relative hazard of death during follow-up and was the strongest association observed in the study.

The result supports looking at physical fitness as multidimensional.

No single test describes the body’s entire functional capacity. Strength, cardiorespiratory fitness, balance, agility and flexibility provide different but complementary information.

6. The relationship between fitness and mortality was graded, but not always linear

Across the fitness assessments and composite index, mortality generally decreased as fitness increased.

However, detailed dose-response analyses showed that the shape of this relationship differed between individual fitness tests and between men and women.

For the composite fitness index, much of the mortality difference was concentrated between the lowest-performing fifth and the higher fitness groups.

This suggests that particularly poor overall fitness may identify an important high-risk group.

It does not establish a specific fitness threshold above which further improvement provides no benefit.

Healthy longevity requires more than surviving without major disease.

It also involves preserving enough physical capacity to move, remain independent and respond to the physical demands of everyday life.

This study provides strong observational evidence that objectively measured physical fitness is associated with survival in adults aged 65 years and older.

Importantly, the association persisted after adjustment for self-reported physical activity.

This suggests that asking “How much do you exercise?” and measuring “What can your body actually do?” provide complementary information.

But the study does not establish causality.

It cannot show that improving a particular fitness test will produce the mortality differences observed between the highest- and lowest-performing groups.

Reverse causation remains possible: underlying disease or early health deterioration may reduce physical fitness before becoming clinically apparent.

Residual confounding is also possible.

Fitness was measured only once, so changes in fitness over time were not assessed.

The study examined all-cause mortality only, not specific causes of death.

Participants had to be sufficiently healthy and mobile to complete the physical tests, creating potential selection toward healthier ambulatory older adults.

Smoking status and direct measures of body composition were unavailable, leaving additional potential for residual confounding.

The findings therefore support physical fitness as a strong prognostic marker of functional health and survival, rather than proving that a particular fitness level directly extends lifespan.

This study demonstrates why physical activity and physical fitness provide different clinical information.

Physical activity describes behavior.

Physical fitness describes measurable physical capability.

A person can report regular physical activity while still having limited strength, balance or cardiorespiratory capacity. Conversely, people reporting similar activity levels can differ substantially in objective physical performance.

This is why the concept of physiological reserve is relevant.

It refers broadly to the body’s capacity to meet physical demands and maintain function under increasing physiological stress.

The study did not directly measure physiological reserve as a separate biological variable. Rather, the authors propose that objective fitness testing may serve as a practical indicator of this underlying functional capacity.

The results also show why fitness should not be reduced to aerobic capacity alone.

Balance and agility, lower-body strength and cardiorespiratory fitness all showed strong associations with survival.

Simple performance-based tests may therefore add useful information to conventional assessment based on diagnoses and reported activity.